Heater



June 26, 1934. F. A. FAHRENWALD 1,954,256

HEATER Filed March 14K, 1932 4 Sheets-Sheet l June 26, 1934. F. A. FAHRENWALD 1,964,256

HEATER Filed March 14, 1932 4 Sheets-Sheet 2 June 26, 1934. F, A FAHRENWALD 1,964,256

HEATER Filed March 14, 1932 4 Sheets-Sheet 3 June 26. 1934. F. A. FAHRENWALD 1,964,256

HEATER Filed March 14, 1932 4 Sheets-Sheet 4 Patented June 26, 1934 UNITED STATES PATENT GFICE.

1S Claims.

My invention relates to heaters, and includes among its objects and advantages increased cheapness, durability, and efficiency in a type of heater employing metallic tubes for the exposure 5 to heat of the fluids to be heated, and usually employing another fluid outside the tubes as a source of heat. It is particularly advantageous for heating gases under pressure, and for work at temperatures where most of the tubes are red hot and not capable of carrying even their own weight in a horizontal position without sagging, or in a vertical position supported from the bottom, without buckling.

In the accompanying drawings:

Y Figure l is a vertical section partly in elevation of a heater according to the invention;

y Figure 2 is a plan view partly broken away of the same heater;

Figure 3 is an end elevation of one of the groups of couplings employed in the heater;

Figure 4 is a section on line 4-4 of Figure 3;

Figure 5 is a view in horizontal cross section on line 5*-5 of Figure 1, showing the spacing of the tubes and the sub-manifold connector.

Figure 6 is a partial section similar to Figure -1 of a modiiied construction;

Figure4 7 is a partial transverse section of the vconstruction of Figure 6;

Figure 8 is a similar section showing another 3o arrangement of tubing;

Figure 9 is an end View of some of the tubing illustrated in Figure 8;

`Figure l is a plan view of part of the tubing of Figure 8;

Figure 11 is a horizontal section similar to Figure on a smaller scale, showing a different Aspacing arrangement with a set or" heat colllectors;

Figure 12 is a section on line 12--12 of Figure A1l;

Figure 13 is a perspective view of the bottom one of a stack of collectors; and

Figure 14 is a side elevation of a power vibrator for cleaning;

In the embodiment of the invention selected for illustration in Figures 1 to 5, inclusive, Ivhave illustrated a relatively large installation comprising a chamber completely enclosed by refractory walls and provided with manholes, or doors, for access to the interior thereof. The left en'd wall l2 is apertured as at 14 so that hot gases may ow or be pumped or forced under `positive pressure, as by the blower 15, through the combustion chamber 17 into that end of the chamber to travel throughout the length thereof lupper ends of the reaches to the exit at 16, which is built up far enough yto direct the hot gases upwardly and avoid injury to workmen, but which has no appreciable action as a discharge stack.

The roof of the chamber is a pavement of individual insulating ceramic units 18 arranged in rows longitudinal of the chamber, each row strung on and supported by a longitudinal T- beam 20 received in grooves in the units 18. Each T-beam 20 is supported at its opposite ends `65 by tension rods 22 extending upwardly to anchor blocks 24 carried on cross beams. The end cross beams 26 are carried directly by the buckstaves 23, and the -central cross beam 30 is supported at each end by a short bridge 32 resting on buck- O staves at 34.

Each individual T-beam 20, together with the insulating units keyed to it, may be individually lifted out from above for inspection or repair.

Within the chamber I have illustrated tubing T5 for operation according to the combined concurrent and countercurrent arrangement described in my earlier Patent Number 1,518,258. Cold fluid enters the manifold 36 at the hot end and ows in concurrent relation with the hot gases through a relatively short portion of the length of the furnace to the outlet manifold 38. Additional cold fluid enters through the manifold 40 at the cold end of the chamber and flows in counter-current relation with respect to the chamber fluids back to the same outlet manifold 38. Both manifolds may receive fluid from a header 41 connected to a pump 43.

From the inlet manifold 40, twenty-one individual serpentine conduits extend to the outlet manifold 33. These conduits constitute the heat transfer area proper. Each conduit is made up of a plurality of vertical reaches 42 extending substantially from the top to the bottom of the chamber. The lower ends of the vertical reaches are interconnected by U-shaped bights 44 formed integrally with the reaches themselves. The are interconnected by fittings according to Figures 3 and 4.

The chamber temperature is a maximum near the inlet 36 and a minimum near the inlet 40. That portion of the tubing and ttings operating at red heat is oiheat resisting alloy, for instance, a steel alloyed with 25% chromium and 12% nickel, which will withstand temperatures up to 1800"7 F. or more for long periods of time. At the cold end near inlet 40 some of the tubing and nttings may be of ordinary steel. 1n intermediate portions of the chamber, alloys suited to the operating temperatures are employed.

Between the manifolds 36 and 38 there are twenty-four conduits of smaller diameter than those between manifolds 40 and 38. The diameters of the two sets of conduits are so proportioned that, with the same pressure head on both inlet manifolds, the desired ratio will obtain between the volumes iiowing through the two sets of conduits. This ratio may advantageously be such that the temperatures of delivery to the manifold 38 are approximately the. same, while the voliunes and velocities in the concurrent section are higher than in the countercurrent section.

Referring to Figures 3 and 4, each fitting comprises a tubular U-shaped body with its open ends facing downwardly. The central one 46 of each group of fittings is provided on one of its legs with laterally projecting lugs 48 on each of which an adjacent plain fitting 50, forming part of the next adjacent conduit, is supported.

From the bight of the fitting 46 an eyelet 52 projects upwardly. The eyelet is offset from the center of the fitting 46 to a position substantially above the center of gravity of the fitting 46 and the side ttings 50. Each fitting 46 is suspended from the roof blocks 18 by a T-shaped hanger 54 having a notch at 56 to receive the eye 52, and a top flange 58. The juxtaposed faces of the roof blocks 18 are grooved to receive the ends of the cross piece 58, and cut away below the grooves to accommodate the shanks of the hangers 54.

Adjacent each manifold, the individual serpentine passages are brought together in groups of three into sub-manifolds 60, each comprising a downwardly facing head 62 provided with three apertures to receive the individual tubes, and iiange or coupling means at 64 for connection to the main manifold. The manifold 40 is directly flange-connected to the adjacent sub-manifolds 60. The manifold 38 is connected with coupling sleeves 66 to two sets of sub-manifolds on opposite sides. The manifold 36 is embedded in the end wall 12 to help keep down the temperature of the upper portion of the wall, and is connected to its sub-manifolds by short, horizontal connecting tubes 68. Above each of the manifolds I have illustrated hand holes '70 for convenient access to the connections to the sub-manifolds.

Each set of three conduits is supported from an individual beam 20 and may be lifted out after disconnecting it from the manifold without disturbing the rest of the unit.

Thus the entire mass of tubing constituting the heat transfer area of the heater, is suspended in tension from above, with individual supports at the top for each vertical reach 42. The hangers 54, in turn, are entirely supported by the insulating roof, and, except for the inlet and outlet manifolds, there is no metallic thermal connection between the inside of the chamber and the outside. The loops of tubing naturally Ytend to hang vertically downward with the reaches 42 perfectly parallel. Whenever high fluid veloci.- tics, or other service conditions, tend to displace them it is a simple matter to lay light spacers in contact with the lower bights.

The suspended reaches 42 terminate at such a level that the bights 44 are spaced above the bottom of the chamber far enough to allow for thermal expansion without any possibility of contact with the bottom of the chamber. Except for the through passage thus left along the chamber bottom, the entire volume occupied by the tubing is uniformly filled with closely spaced tubes in quincunx arrangement as shown in Figure 5, each tube having four other tubes spaced from it a distance approximately equal to half of the diameter of a tube.

A plurality of baffles 72 project upwardly from the bottom of the furnace, and cut off the through passage at frequent intervals thus compelling the main flow of the chamber fiuids to pass between the tubes. The bights 44 are thus all located in pockets between the baies 72, in which pockets relatively cool fluid may accumulate. Thus the bights 44 do not carry as heavy a load of heat transfer as the vertical reaches 42 and the cooling action of the iiuid inside the tubes may keep the bights 44 a little cooler than the vertical reaches.

In Figure 6 I have indicated an inlet manifold 74 located above the roof '76 and delivering into individual horizontal tubes 78 running longitudinally of the chamber just below the roof, throughout the length of the stack of tubing. The tubes 78 may be supported as at 80 at the. ends remote from the inlet manifold and communicate with sinuous tubing 82 with each upper bight hung from the tube 78 by links 84. The sinuous tubing 62 thus returns the fluid entering through the tube 78 to the same end of the chamber where it entered to be delivered through an outlet manifold 85.

Referring to Figure 7, the roof of Figure 6 may be removed as a unit by sliding on tracks 87, together with all the manifolds and tubings suspended therefrom, or lifted vertically out of the chamber. The wheels 89 on the ends of the cross members 91 support the weight of the roof and tubing when it is slid out. bled, sealing bricks 93 are simply laid in place to complete the enclosure.

In Figure 8 I have illustrated an individual inlet tube S6 in a position similar to the tube 78 of Figure 6 with the sinuous tubing hung direct-- ly over the tube 86, which may be iiattened as clearly indicated at 88 to increase its strength as a supporting beam. Each tube discharges through a tting into the sinuous tubing 92. The ttings rest on the wall 94 through which the hot gases enter. and each fitting comprises a mouth 96 receiving the end of tube 86, an upwardly extending portion 98 and a rearwardly extending portion 100 terminating in a downwardly opening mouth 102 to receive the end of the tubing 92. The portion 93 or the portion 100, or both, incline laterally, as clearly indicated in Figure 9. to support the first vertical reach of the tubing 92 beside the tube 86. Subsequent upper bights or fittings in the tubing are looped over the tube 86 diagonally, and the different sets of tubing 86 and 92 are arranged, as clearly indicated in Figure l0, with the vertical reaches of each set interpolated between the vertical reaches of adjacent sets. as close as that of Figure 5 may readily be obtained, in which the tubing itself occupies substantially 25% of the4 volume of the chamber.

The roof 103 of Figure 8 may be mounted as in Figure 7 for removal without the tubing.

Each group of three conduits in Figures l and 2 is insulated from end to end from any parallel passage for electrical current, and may therefore be employed as a resistance unit for delivering heat tc the fiuid flowing through it, the heat A being generated in the material of the tubes themselves.

Referring to Figure 2 I have indicated a transformer at 104 with its low potential terminals connectedto the manifolds 40 and 38. This is When assem- In this way a spacing l? liu-il) -ber gases.

Vtubes themselves are cooled by the gases inside them, they cannot radiate heat to each other for any useful purpose.

According to Figures 11, 12, and 13, the tubes are intermeshed with ceramic heat collectors, which may become heated to substantially the 'temperature of the chamber gases and deliver considerable amounts of heat to the metallic tubes 'by direct radiation. Each individual collector 110 comprises side walls with a relatively small central aperture at 112, and cross pieces at the corners defining an aperture 114, large enough to enable the box to be slipped up over one of the bights 44, even in cases where U- shaped fittings are used in lieu of such bights. Thus, a stack of radiation units 110 may be slipped up on a pair of reaches 42, and by putting in a key brick 116 through the side holes in the lowest radiation unit, the entire stack is fastened in place.

By selecting certain pairs of the vertical reaches to carry collector units, as indicated in Figure 11, a substantial portion of the space surrounding practically every tube, can be bounded by material of high emissivity, with a corresponding increase in the rate at which, at any predetermined temperature for the heating gases, heat will penetrate into the metal of the tubes.

Such an arrangement of tubing as that disclosed, lends itself peculiarly well to cleaning by vibration alone. In Figure 14 I have illustrated a high frequency electrically actuated hammer 118 provided with an impact member 120, a handle 122, and a contact switch 121i. Such a unit in which the impact member vibrates with a frequency of the order of magnitude of 450 vibrations per second, can be pressed rmly against almost any portion of the dangling loops of pipe,

, and impress upon them a vibration that will travel through a considerable number of adjacent loops and effectively dislodge and shake off ne particles lying on or adhering to either the outer or inner surfaces of the tubing, or even heat-resisting films or skins formed on either the outer or inner surfaces of the tubing by deposition or by reaction between the fluids and the surface of the metal.

When the fluid to be heated is a gas, I employ high linear velocities inside the tubing. These velocities are many times greater than the critical velocity for turbulent iiow in the tubing, and are preferably so high that the pressure drop through the tubing is substantially the same as it would be at the same speed if the tubing were straight instead of sinuous.

An interesting characteristic of the action of such rapid fiow has been found to be that practically any gaseous material will keep the inner surfaces of the tubes scoured and cleaned. Under certain circumstances I employ velocities such that no solid material in particles small enough to be mechanically able to pass through the tubing, will ever be retained at any point in the tubing. In other words, small metal bodies, such as ball bearings, are carried up the vertical reaches because the upward velocity of the gases exceeds the maximum downward velocity with which such particles can fall through the gas in which they nd themselves.

Without further elaboration, the foregoing will so fully explain my invention, that in the future vothers may readily adapt the same for use under various conditions of service, by applying knowledge current at the time of such adaptation.

I claim:

1. In a heat interchanger, a chamber having a removable roof, and tubing in said chamber suspended in a plurality of vertically depending U- shaped bights, said suspended tubing being supported by said roof and removable therewith.

2. In a heat interchanger, insulation defining a chamber, vertical tubing housed inside said chamber, and tension means suspending said tubing entirely from said insulation.

3. In a heat interchanger, insulating walls including a roof, tubing housed inside said walls and supported entirely by said roof, said tubing lying entirely below the lower surface of said roof.

4. In a heat interchanger, insulating walls including a roof, tubing housed inside said walls, and tension means supporting said tubing entirely from said roof, said tubing terminating below the lower surface of said roof, said tension means terminating below the upper surface of said roof.

5. In a heater, a chamber for hot uid, an inlet for cold fiuid, a tube lying close under the chamber roof and receiving fluid fromsaid inlet, and K serpentine tubing receiving the uid from said tube and supported by said tube.

6. A heater unit comprising arelatively straight conduit portion and a serpentine portion, the

A-iio loops of said serpentine portion being connected Y conduit portion and a serpentine portion, the

loops of said serpentine portion being in substantially the same plane as, and connected to, said relatively straight portion at a plurality of points to be supported thereby.

9. A heater conduit comprising a relatively straight conduit portion and a serpentine portion, the loops of said serpentine portion being connected to said relatively straight portion to be supported thereby.

10. A heater conduit comprising a relatively straight conduit portion and a serpentine portion in series therewith, said serpentine portion being connected to said relatively straight portion at a plurality of points to be supported thereby.

11. A heater conduit comprising a relatively straight conduit portion and a serpentine portion in series therewith, said serpentine portion being connected to said relatively straight portion at a plurality of points to be supported thereby, and means for passing a fluid to be heated first through said straight portion and then through said serpentine portion.

12. A heater unit comprising tubing to receive fluids to be heated, a chamber enclosing said tions of said tubing receiving the incoming cold fluid lying under and closely adjacent to said roof and supporting said roof.

13. A heater comprising a structural frame "work, conduit units each comprising a relatively straight portion, a serpentine portion suspended 15. A heater conduit comprising a relatively straight portion, a serpentine portion having loops, and supporting connections for supporting said loops from said relatively straight conduit portion, and at the same time permitting relative thermal expansion between said loops and said relatively straight conduit portion.

16. A heater comprising a supporting structure, a relatively straight conduit portion, connections for supporting said conduit portion on said structure, leaving the conduit portion free to contract and expand, a serpentine conduit portion having loops, and supporting connections for supporting said loops from said relatively straight conduit portion, and at the same time permitting relative thermal expansion between said relatively straight conduit portion and said serpentine conduit portion. v

FRANK A. FAHRENWALD. 

